This plaque by the canal at Broome Bridge marks the spot where Sir William Rowan Hamilton, arguably Ireland’s greatest scientist, invented a revolutionary new algebra in 1843.

His ‘quaternions’ describe things moving in 3D, and are now used to orient spacecraft, in 3D animations and computer games. You could say that they helped to land a man on the Moon! They also broke the fundamental commutative law of multiplication.

Hamilton lived and worked nearby, at Dunsink Observatory, and made important contributions to dynamics, the foundations of quantum mechanics, and optics.

Facilities, visiting: the plaque is by the canal, at the railway bridge. Each year, there is a commemorative walk from Dunsink Observatory along the canal to Broom Bridge on October 16, the anniversary of the date when Hamilton invented quaternions. There are no facilities at Broome Bridge, but if you stroll the 3km west along the canal to Ashtown, there is a coffeshop.